High amylose starch and resistant starch fractions

ABSTRACT

Starch, particularly maize starch, having an amylose content of more than 80% w/w, including physically or chemically modified derivatives thereof, and destructurized and non-destructurized forms thereof. Also, disclosed are hybrid maize seeds capable of producing a starch having an amylose content of more than 80%. Also disclosed are starch fractions of enhanced dietary fiber and/or resistant starch content.

TECHNICAL FIELD

This invention relates to high amylose content starch, in particular toa maize starch having an amylose content of more than 80% w/w. Theinvention further relates to single, double and multiple cross maizehybrids, particularly to a maize single cross F1 hybrid, capable ofproducing grain having such a high amylose content and to this grain.

The invention still further relates to fractions of high amylose starchthat are enriched in dietary fiber and resistant starch content whilstclaiming a high amylose content.

BACKGROUND ART

Most common starches contain approximately 25% amylose and 75%amylopectin. Amylose is a linear glucose polymer fraction, whilstamylopectin is a branched glucose polymer fraction.

In the prior art, it has been recognized that currently availablecommercial starch having an elevated amylose content would impartcertain desirable properties to various compositions including films,foods and industrial products. Accordingly, attempts have been made inthe prior art to produce high amylose content maize. This is exemplifiedin AU-A-45616/89 wherein a maize seed deposited as ATCC No. 40499 isdisclosed as capable of yielding a starch having an amylose content ofup to 72%.

Typically, however, a commercial starch having an amylose content of55-65% would be regarded in the art as having a high amylose content.

The present inventors whilst recognizing the utility of the commerciallyavailable so-called high amylose starches, have sought to produce amaize having a still higher amylose content.

DISCLOSURE OF INVENTION

In the course of a breeding program, a single cross F1 hybrid maize seedwas produced, which carried the ae amylose extender gene. This seed wasfound to be capable of producing grain, in which the amylose content ofthe starch derived therefrom was in excess of 80%.

Accordingly, in a first aspect, this invention consists in a hybridmaize seed capable of producing a starch having an amylose content ofmore than 80%.

In a second aspect, this invention further consists in a maize starchhaving an amylose content of more than 80%, physically or chemicallymodified derivatives thereof, and destructurized and non-destructurizedforms thereof.

In a third aspect, this invention still further consists in compositionsincluding a maize starch selected from the group consisting of maizestarch having an amylose content of more than 80%, physically orchemically modified derivatives thereof and destructurized andnon-destructurized forms thereof.

In a fourth aspect, this invention still further consists in a processfor the formation of a composition comprising including a maize starchselected from the group consisting of maize starch having an amylosecontent of more than 80%, physically or chemically modified derivativesthereof and destructurized and non-destructurized forms thereof, in saidcomposition.

In a fifth aspect, the present invention still further consists in ahybrid maize seed resulting from a cross between any of the parentallines selected from the group consisting of G112, G113, G116, G117,G118, G119W, G120, G121, G122, G125W, G126, G128, G129, G135W, G136W,G138W, G139W, G140W and G144, said hybrid maize seed yielding a starchhaving an amylose content of more than 80%.

Starch granules from any botanical source are a heterogeneous mixturevarying in physiological age and this affects their physical size,structure and properties. If the starch granules are physicallyseparated according to their granule size, it has been noted by a numberof authors that the properties of each size fraction are somewhatdifferent. For example, Cluskey et al in Starke, 32, 105-109(1980)reported on the fractionation of dent corn and amylomaize starchgranules. They found that an inverse relationship existed betweengranule size and iodine binding capacity in the amylomaizes. Thus, thepercent apparent amylose found in the fractions of amylose V starchamounted to 40% for the largest size particles and 52% for the smallestparticles.

The correlation between amylose content and size fraction has beenobserved by the present inventors in relation to high amylose starchesof the type mentioned above and in co-pending patent application PL6537.

In this latter mentioned patent application, PL6537, it was disclosedthat high amylose starches have a high dietary fiber or resistant starchcontent. More specifically, it was found that there was a correlationbetween amylose content and dietary fiber/resistant starch such thatincreasing levels of amylose above 55% were associated with increasinglevels of dietary fiber/resistant starch.

Patent application PL6537 further disclosed the useful nature of suchstarches in the preparation of food compositions having an enhanceddietary or resistant starch content.

Based on the observations of

(1) an association of dietary fiber and resistant starch with increasinglevels of amylose; and

(2) increasing amylose content with decreasing starch granule size,

it was to be expected that decreasing starch granule size fractions ofhigh amylose starch would be associated with enhanced levels of dietaryfiber and resistant starch.

Surprisingly, this was found to be incorrect. In fact it was found thatthere is an optimum starch granule size fraction which is intermediatein size and not necessarily associated with the highest amylose contentfraction.

Accordingly in a sixth aspect, the present invention still furtherconsists in a starch fraction of enhanced dietary fiber and/or resistantstarch content comprising a high amylose starch which has beenfractionated according to granule size to yield a fraction which ischaracterised by a dietary fiber and/or resistant starch content whichis greater than said high amylose starch.

In a seventh aspect, the present invention still further consists in afood composition having an enhanced dietary fiber and/or resistantstarch content, including a starch fraction of enhanced dietary fiberand/or resistant starch content derived from a high amylose starch whichhas been fractionated according to granule size to yield a fractionwhich is characterised by a dietary fiber and/or resistant starchcontent which is greater than said high amylose starch.

For the purpose of the description of this invention, "high amylose"means an amylose content (dsb) of 50% or more, preferably 70% or more,most preferably 80% or more. Particularly preferred amylose contents are85% or more and 90% or more.

For the purposes of the description of the invention, the method bywhich amylose was determined is set out below.

METHOD: Apparent Amylose (Blue Value)

SCOPE: High Amylose Maize Starch

APPARATUS:

Defatting

Soxhlet extraction apparatus

Steam bath

Whatman thimbles, 25×80 mm

Drying Oven 105° C.

Dessicator

Amylose Determination

Stoppered 50 ml test tubes

Vortex mixer

Boiling Water bath

Spectrophotometer (650 mm, slit width 0.2 mm)

REAGENTS:

Defatting

Methanol (AR Grade)

Amylose Determination

Dimethylsulfoxide (HPLC Grade)

Iodine/Potassium iodide solution

3.0 g iodine and 30 g potassium iodide made up to 1000 mls with 0.1 Nsodium hydroxide

Methanol (AR Grade)

Amylose (Sigma Cat. No. A0512)

Dried for 2 hours at 105° C. prior to use.

PROCEDURE:

Defatting

(1) Weigh 5 grams of starch into the thimble.

(2) Place the thimble in the Soxhlet apparatus.

(3) Extract the sample with methanol (200 mls) for 20 hours.

(4) Recover the thimble and dry in an oven at 105° C. for 12 hours.

Amylose Determination

(1) Accurately weigh starch (100.0 to 105.0 mg) into the text tube.

(2) Add methanol (1 ml) and vortex mix.

(3) Add DMSO (15 mls), invert the test tube, and vortex mix.

(4) Place the test tubes in a vigorously boiling water bath for 60minutes.

(5) Invert and vortex mix each test tube at 15 minute intervals duringthis period.

(6) Add distilled water (15 mls), invert and vortex mix. Place the testtube in the boiling water bath for a further 30 minutes.

(7) Quantitatively transfer the contents of the test tube to a 100 mlvolumetric flask (use a funnel in the flask). Make the solution tovolume with distilled water.

(8) Transfer an aliquot (3 mls) of this solution to a 100 ml volumetricflask and add 90 mls of distilled water.

(9) Add Iodine/Potassium Iodide solution (1 ml) to the diluted solutionand immediately shake and mix thoroughly. Make to volume with distilledwater.

(10) Measure the absorbance of this solution at 605 nm compared to ablank consisting of Iodine/Potassium Iodide solution (1 ml) diluted to100 mls with distilled water in a volumetric flask.

CALCULATIONS:

For native starches: ##EQU1##

The method by which starch was separated from the maize grain was asfollows:

1. Prepare 200 g meal by grinding through the 2 mm then the 1 mm screenof one Retsch Mill.

2. Wet thoroughly, stirring by hand, with 600 ml 0.1 N NaOH.

3. Add 2,200 ml 0.1 N NaOH and blend 5 minutes at 2/3 speed with theUltra Turrax.

4. Sieve over 44u screen.

5. Return sieve overs with 1 L water and blend for another 3 minutes, ifnecessary.

6. Sieve over 44u screen.

7. Centrifuge filtrate at 3000 rpm for 15 minutes. Decant. Wipe out theneck of the bottle with a tissue to remove fat.

8. Reslurry starch (centrifugate) with 200 ml water, i.e. 50 ml in eachof 4 tubes. Centrifuge.

9. Remove starch from centrifuge tubes with about 250 ml water.

10. Adjust pH of starch slurry to 6.0-6.5 with 0.5 N HC1. Filter againover 44u screen, if necessary.

11. Buchner filter and air dry.

MODES FOR CARRYING OUT THE INVENTION

In order to better understand the nature of this invention, a number ofexamples will be described.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a gel permeation chromatography molecular weight profile of anumber of maize starches;

FIG. 2 is a viscograph of a number of maize starches in water;

FIG. 3 is a viscograph of a number of maize starches in base; and

FIG. 4 is a graph of total dietary fiber versus average starch granulesize.

Maize Seed

A range of parental lines of maize seeds were obtained from High YieldSeed Co, Tamworth, Australia. Non-limiting examples of these parentinglines included G112, G113, G116, G117, G118, G119W, G120, G121, G122,G125W, G126, G128, G129, G135W, G136W, G138W, G139W, G140W, and G144.

Hybrids were produced by crossing inbred lines carrying the ae amyloseextender genes. These inbred lines were selected for combining abilityand identified as specific female and male parents to produce thehybrids. Conventional breeding methods and techniques were used indeveloping inbred lines with repetitive amylose assays to ensure thetransfer of recessively inherited ae gene.

One particular cross between male G116 and female G121 resulted in a F1hybrid, referred to as Code 008 and deposited with the American TypeCulture Collection (ATCC), 12301 Parklawn Drive, Rockville, Md. 20853,U.S.A., under the designation 75182 on 15 Jan., 1992. This hybridyielded grain the starch of which was found to have an amylose contentin excess of 80%.

Based on the disclosure of this invention, the person skilled in the artwould expect that hybrids resulting from further crosses of the parentallines mentioned above will yield starch having an amylose content inexcess of 80%.

In fact experimental hybrids have yielded starches obtained from crossesbetween the above mentioned parent lines having high amylose contents.Set out below is a summary of the relevant crosses with amylose contentin % bracketed.

    ______________________________________                                        FEMALE       MALE        HYBRID                                               ______________________________________                                         1.  G117 (81.6)                                                                           G116 (82.2) G117 × G116 (83.3)                              2.  G116 (82.2)                                                                           G122 (89.6) G116 × G122 (80.5)                              3.  G118 (94.3)                                                                           G122 (89.6) G118 × G122 (85.9)                              4.  G120 (94.6)                                                                           G122 (89.6) G120 × G122 (80.4)                              5.  G122 (89.6)                                                                           G120 (94.6) G122 × G120 (81.9)                              6.  G122 (89.6)                                                                           G140 (92.2) G122 × G140 (85.4)                              7.  G128 (71.5)                                                                           G129 (61.8) G128 × G129 (82.8)                              8.  G140 (93.2)                                                                           G121 (94.7) G140 × G121 (93.0)                              9.  G140 (92.2)                                                                           G144 (60.4) G140 × G144 (85.3)                             10.  G139W (71.9)                                                                          G136W (93.4)                                                                              G139W × G136W (95.7)                           11.  G121 (94.7)                                                                           G126 (82.2) G121 × G116 (85.0)                             ______________________________________                                         * W = White seed.                                                        

Experiments conducted using Code 008 seed have shown that the climaticand agronomic conditions under which the maize is grown will have asignificant effect on the amylose content. Specifically, it has beenfound that seed cultivated under irrigation near Tamworth, Australia(latitude 31.1° S) in an early crop and a late crop yielded starchhaving an amylose content respectively of 85.0% and 90.1%. Similarly, acrop cultivated at Finley, Australia (latitude 35.6° S) yielded starchhaving an amylose content of 94.8%. By contrast, the same seed whencultivated under irrigation at Giru, Australia (latitude 19.5° ) yieldeda starch having an amylose content of 78.6%.

Accordingly, a preferred embodiment of this invention comprises a maizeseed deposited with the ATCC and designated 75182.

A further preferred embodiment of this invention comprises a maizestarch having an amylose content of 85.0% or more, most preferably 90.1%or more.

To further characterize the maize starch derived from Code 008 grain,molecular weight profiling by gel permeation chromatography has beenperformed. The method by which this was done is set out below whilst theresults are shown in the accompanying FIG. 1. For comparative purposes,two commercially available maize starches, HA Class V and HA Class VIIare shown.

METHOD: Gel Permeation Chromatography of Starch

SCOPE: Starch

APPARATUS:

Sample Preparation

Screw capped test tubes (50 ml)

Boiling water bath

Microcentrifuge (Eppendorf 5415)

Desiccator

    ______________________________________                                        HPLC                                                                          ______________________________________                                        Column         Alltech GPC High MW Polar 5U                                                  (Cat. No. 100586)                                              Detector       Waters 410 Refractive Index                                                   Detector (X 128 35° C.)                                 Pump           Waters 600 E                                                   Injector       Waters 712 WISP                                                Column Heater  (Set at 25° C.)                                         Software       Maxima 825 (V 3.3)                                             ______________________________________                                    

REAGENTS:

Dimethyl sulfoxide (Chrom AR HPLC Grade - Mallinckrodt)

Dimethyl formamide (Chrom AR HPLC Grade - Mallinckrodt)

Pullulan Molecular Weight Standards - Showa Denko (ex EdwardInstruments)

HPLC Mobile Phase - DMSO:DMF (20:80)

SAMPLE PREPARATION:

Standards

(1) The pullulan molecular weight standards need to be weighed into thescrew capped test tubes in the following manner:

Tube 1- 5.0 mg each of P800, P100, P10 and glucose

Tube 2- 7.0 mg each of P400, P50 and P5

Tube 3- 7.0 mg each of P200, P20 and maltotriose.

(2) Add DMSO (4 mls) to each tube and tightly seal it.

(3) heat the tubes in the boiling water bath for 5 minutes to dissolvethe pullulan.

(4) Remove and cool the test tube to room temperature.

(5) Add DMF (16 mls) and mix well.

(6) Place 3×1.5 ml aliquots into microcentrifuge tubes and centrifuge at14000 rpm for 10 minutes.

(7) Remove the top 1 ml of solution from each centrifuge tube and placein a WISP vial.

Samples

(1) Accurately weight the sample (50.0 mg) into a screw capped testtube.

(2) Add DMSO (10 mls).

(3) Heat in a boiling water bath for 60 minutes.

(4) Remove and cool the test tube to room temperature.

(5) Add DMF (40 mls) and mix well.

(6) Place 3×1.5 ml aliquots into microcentrifuge tubes and centrifuge at14000 rpm for 10 minutes.

(7) Remove the top 1 ml of solution from each centrifuge tube and placein a WISP vial.

HPLC Preparation

(1) Prior to fitting the column, pump water (100 mls) through the HPLC.

(2) Prepare the mobile phase and pump 50 mls through the HPLC. Ensurethat the WISP is purged during this stage.

(3) Adjust the flow rate of 0.2 ml/minute and connect the column.

(4) Allow the column to equilibrate overnight.

(5) Prior to the injection of samples, purge the WISP and then graduallyincrease the flow rate to 1.5 mls/minute.

(6) Set the column heater to 25° C.

(7) Inject the standards and samples- 100 μl injection volume.

(8) After samples have been analysed turn the column heater off andreduce the flow rate of 0.2 mls/minute.

(9) Disconnect the column.

(10) Wash the system with water overnight at 0.5 mls/minute.

(11) Wash the system with methanol (200 mls).

Viscographs have also been prepared comparing maize starch from Code 008(designated Gelose 80) with Gelose 50 and Gelose 70. FIG. 2 shows theviscosity profile under alkaline conditions whilst FIG. 3 shows theviscosity profile in water.

Maize Starch

The maize starch of the first aspect of this invention having an amylosecontent of more than 80% may be used in a variety of compositions knownin the art. The usefulness of the starch is believed to be a result ofthe higher content of more linear molecules. This seems to impartphysical properties which tend towards those of conventionally usedsynthetic plastics materials. Consequently, films formed from the starchof the invention have higher tensile strengths and are good oxygenbarriers. The starch is also easier to process on existing syntheticplastics materials equipment such as blow molding and injection moldingmachines.

Furthermore, this starch may be physically modified or chemicallymodified to produce a variety of derivatives well known in the art.These starches may also be used in a variety of compositions.

Finally, this starch may also be used in processes and compositionsrequiring the starch to be destructurized within the meaning of thatterm defined in EP0118240.

Some non-limiting examples of compositions in which the maize starch ofthis invention in all of its forms, could be used include:

1. Corrugating adhesives.

2. Sausage skins.

3. Confectionery.

4. Other food compositions where the enhanced gel strength of the starchwould be advantageous.

5. Films, either alone or laminated with polymers such asethylenevinylalcohol to achieve both gas and water barrier properties.

6. Biodegradable and controlled release matrices and methods for formingand using these matrices as disclosed in PCT/AU90/00422, the contents ofwhich is incorporated herein by way of reference.

7. Shaped articles, processes for forming shaped articles and methodsfor using shaped articles as disclosed in PCT/AU90/00237, the contentsof which is incorporated herein by way of reference.

8. Coextrusions with synthetic polymers.

9. Intermediate products such as pellets and rods, formed for example byextrusion, and including combinations of starch with one or more naturalor synthetic polymers, plasticizers, colourants and other additives.

10. Other blends of starch with natural or synthetic polymers to obtainenhanced structural properties.

Starch Fractions

The starches of the sixth and seventh aspects of this invention mayoriginate from a number of sources including cereals such as maize,barley, wheat and legumes, providing that the starch content of suchsources is high in amylose.

To fractionate the starch granules, there are a number of methods knownin the art including dry powder sieving, hydrocyclone classification,air classification and differential sedimentation. A person skilled inthe art would be readily able to choose an appropriate method dependingon the source material and other relevant factors.

Although the size fraction of enhanced dietary fiber and/or resistantstarch may vary, the example that follows describes the work that wasdone by the present inventors in relation to a maize starch sample.Based on this disclosure, a person skilled in the art could readilyrepeat this work using other starch sources to identify an appropriatefraction.

Once the starch has been appropriately fractionated, the fractionshaving enhanced dietary fiber and/or resistant starch content may beprocessed to obtain starch having further increased dietary fiber and/orresistant starch content using entirely conventional methods well knownin the art. An example of the fractionation will now be described.

Fractionation of Maize Starch by Granule Size

A high amylose maize starch--High Amylose 80(10/91) was fractionatedinto seven subsamples based on granule size using the aqueousdifferential sedimentation procedure described by Cluskey et al (1980).This method was chosen since it minimised damage to the starch, did notintroduce any residues and it was indicated that exposure of the starchgranules to distilled water for long periods of time did not affecttheir integrity. Each subsample was weighed, measured for averagegranule size and the apparent amylose content, total dietary fiber andresistant starch determined. Each starch sample (60 grams) was separatedinto the seven fractions which were freeze-dried and weighed on aMettler PE 3600 top pan balance. A scanning electron microscope was usedto visually check the uniformity of the size distribution of thegranules in each fraction.

Each fractionated starch sample was analysed for granule size accordingto the method described below. Apparent amylose content was determinedusing the method described above. Dietary fiber and resistant starch(McCleary et al) were determined using the methods disclosed inco-pending application PL6537.

Granule size was determined using a Malvern Master Sizer which utilisesa He--Ne laser (632.8 nm) with a maximum output of 5 mW CW. In thismethod a starch slurry was made using approximately 15 mL of distilledwater in a 50 mL beaker. The slurry was sonicated for 4 minutes. Theslurry was then introduced into the stirred cell and the obscurationvalue adjusted using distilled water to 0.20. The slurry was allowed tostir for a further 2 minutes before readings were taken. Four readingswere taken for each sample in order to check the stability of thereadings being obtained.

Results

In Table 1 set out below, there is shown the results (the average of twoseparate fractionations, together with the range of analytical results)obtained for each of seven particle size fractions. These results aregraphically presented in FIG. 4, from which it is particularly evidentthat the level of resistant starch and dietary fiber is significantlyincreased between the second and fifth fractions, ie, 10.2-7.6 microns.Thus, if those starch fractions were to be segregated from the originalstarch sample, only 46.9% of the solids would need to be removed toproduce a fraction in which the resistant starch was increased by 36%and dietary fiber by 24%.

Although the starch fractions of the invention are

                  TABLE 1                                                         ______________________________________                                        Fractionation of High Amylose 80 (10/91) Maize Starch by Granule Size                               Apparent Total                                          Amount in   Average   Amylose  Dietary                                                                              Resistant                               Fraction    Granule Size                                                                            Content  Fibre  Starch                                  (%) dsb     (microns) (%) dsb  (%) dsb                                                                              (%) dsb                                 ______________________________________                                        High   100.00   10.0      85     33.4   18.1                                  Amylose                                                                       80 - 10/91                                                                    Fraction 1                                                                           35.6 ± 1.1                                                                          12.3 ± 0.5                                                                           80 ± 0                                                                            31.4 ± 1.5                                                                        17.7                                  Fraction 2                                                                           15.0 ± 2.6                                                                          10.2 ± 0.1                                                                           83 ± 1                                                                            38.3 ± 2.0                                                                        16.4                                  Fraction 3                                                                           13.0 ± 1.1                                                                          9.1 ± 0.2                                                                            85.5 ± 0.5                                                                        41.3 ± 0.3                                                                        22.8                                  Fraction 4                                                                           14.9 ± 1.0                                                                          8.3 ± 0.1                                                                            85.5 ± 0.5                                                                        39.4 ± 4.1                                                                        24.6                                  Fraction 5                                                                           10.2 ± 1.6                                                                          7.6 ± 0.1                                                                            88.5 ± 0.5                                                                        37.2 ± 1.3                                                                        18.9                                  Fraction 6                                                                            7.0 ± 1.6                                                                          7.2 ± 0.1                                                                            89.5 ± 0.5                                                                        31.3 ± 2.4                                                                        21.7                                  Fraction 7                                                                            4.3 ± 2.7                                                                          6.8 ± 0.2                                                                            89     28.1   10.1                                  ______________________________________                                    

high in dietary fiber and/or resistant starch, it should also beappreciated that another important property is that these fractions are"naturally" derived. This arises out of the fact that the fractions areprepared using a physical means of separation. No chemical or othertreatments are required in order to produce starch fractions having ahigh dietary fiber and/or resistant starch content. Such a property isof particular importance in food applications in that no regulatoryapproval would be required in order to incorporate such materials infood compositions.

The person skilled in the art will readily appreciate that the starchfractions of the invention having the enhanced dietary fiber and/orresistant starch content may be used in a variety of food compositions.Such uses are disclosed, for example, in co-pending application NoPL6537.

Whilst it is not as yet known why the fractions of the invention haveenhanced dietary fiber and/or resistant starch content, it will beappreciated by persons skilled in the art that numerous variationsand/or modifications may be made to the invention as described withoutdeparting from the spirit or scope of the invention as broadlydescribed. Accordingly, the Example based on a sample of high amylosemaize starch is to be considered in all respects as illustrative and notrestrictive.

The person skilled in the art will readily appreciate that the maizestarch of the invention both in its native form, and the other formsmentioned above will have many applications additional to thosementioned.

It will also be appreciated by those skilled in the art that numerousvariations and modifications may be made to this invention withoutdeparting from the spirit or scope thereof as broadly described.

We claim:
 1. A maize starch selected from the group consisting of maizestarch having an amylose content of more than 80%, physically orchemically modified derivatives of maize starch having an amylosecontent of more than 80%, destructurized maize starch having an amylosecontent of more than 80%, and non-destructurized maize starch having anamylose content of more than 80%.
 2. A maize starch as in claim 1 havingan amylose content of 85.0% or more.
 3. A maize starch as in claim 2having an amylose content of 90.1% or more.
 4. A maize starch as inclaim 3 having an amylose content of 94.8% or more.
 5. A compositioncomprising a maize starch selected from the group consisting of maizestarch having an amylose content of more than 80%, physically orchemically modified derivatives of maize starch having an amylosecontent of more than 80%, destructurized maize starch having an amylosecontent of more than 80%, and non-destructurized maize starch having anamylose content of more than 80%.
 6. A composition as in claim 5 whereinthe maize starch has an amylose content of 85.0% or more.
 7. Acomposition as in claim 6 wherein the maize starch has an amylosecontent of 90.1% or more.
 8. A composition as in claim 7 wherein themaize starch has an amylose content of 94.8% or more.
 9. A starchfraction of enhanced dietary fiber and/or resistant starch contentcomprising a high amylose starch, the amylose content of which is 50% ormore, which has been fractionated according to granule size to yield afraction which is characterised by a dietary fiber and/or resistantstarch content which is greater than said high amylose starch prior tofractionation.
 10. A starch fraction as in claim 9 wherein the highamylose starch is selected from the group consisting of maize, barley,wheat and legumes.
 11. A starch fraction as in claim 10, wherein theamylose content of the high amylose starch is 70% or more.
 12. A starchfraction as in claim 11, wherein the amylose content of the high amylosestarch is 80% or more.
 13. A starch fraction as in claim 12, wherein theamylose content of the high amylose starch is 85% or more.
 14. A starchfraction as in claim 13, wherein the amylose content of the high amylosestarch is 90% or more.
 15. A starch fraction as in claim 9 wherein thefractionation is by dry powder sieving, hydrocyclone classification, airclassification or differential sedimentation.
 16. A starch fraction asin claim 10 wherein the dietary fiber content of the fraction isincreased by about 24% or more and the resistant starch content of thefraction is increased by about 36% or more over the high amylose starchprior to fractionation.
 17. A starch fraction as in claim 9 wherein theaverage granule size of the fraction is from about 10.2 to 7.6 microns.18. A food composition including a starch fraction as claimed in claim9.